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Fall look a sign of tree trouble PDF Print E-mail
Feature
Written by BILL SCHANEN IV   
Wednesday, 11 September 2013 21:23

Port’s grand maples are withering and, in some cases, dying because of what experts say is a perfect storm of factors, starting with the drought

    It’s only the second week in September, but look at many of Port Washington’s partially bare trees and you would think it was late fall.

    The city, whose ash trees are already under assault from the emerald ash borer, is now watching its maple trees wither and, in some cases, die.


    There’s no single culprit as in the case of the emerald ash borer. Rather, a number of conditions and diseases are taxing maple trees of various varieties and sizes, experts said.


    It is a perfect storm for some of the city’s most magnificent trees.


    “That’s really what it is — the perfect storm,” said Jon Crain, the city’s arborist. “There’s a number of factors at work here, starting with stress from last year’s drought.”


    Add to that a number of funguses that have taken hold in compromised trees and planting mistakes made decades ago and you start to understand why some maples leaves appear to be dying on the branch and falling far too early.


    “There’s usually not one easy answer to problems like this, but it starts with the drought, and we’ll continue to see the effects of a diminished water supply,” said Olivia Witthun, the Wisconsin Department of Natural Resources’s urban forestry coordinator for the east-central region, which includes Ozaukee County.


    “Stress from the drought sets trees like maples up for a number of other problems, which is why we’re seeing trees lose their leaves early and grow them late.”


    One of the problems that has become more evident in Port’s weakened maples, Crain said, is stem girdling roots, a condition in which trees that were planted too deep strangle themselves with their roots.


    “This is something that occurs when trees were put in too deep and the roots work their way to the surface and wrap around the tree, causing a slow death,” Witthun said.


    Some varieties, such as Norway maple, which constitutes a significant portion of the city’s maple inventory, have relatively shallow root systems and are particularly susceptible to girdling roots, Crain said.


    “At one time, the city thought Norway maples would make good street trees,” he said. “Now we’re trying to diversify and only plant one species of maple.”


    Among the other problems plaguing trees is an ironic result of weather extremes. Trees weakened by drought suffered another blow in the form of a wet spring that instead of reversing the effects of moisture depravation proved to be an ideal incubator for a variety of funguses, starting with maple tar spot fungus.


    The fungus, which appears as dark, tar-like spots on the leaves of maples, is prevalent throughout the city. And while it is generally considered not to be particularly harmful, it contributes to the withered look of the city’s maple stock.


    “It’s mostly just unsightly,” said Mike Wendt, an instructor of arboriculture and horticulture at Milwaukee Area Technical College, whose students will be in Port Washington later this week cutting down ash trees killed by the emerald ash borer. “Leaves may fall a little earlier, but all in all, tar spots don’t affect the tree to a great extent, although over many years it might.”


    Another problem with the city’s maples is verticillium wilt, Crain said.


    Verticillium wilt, which affects a number of tree species, is caused by a soil-borne fungus that creates toxins that attack a tree’s water-conducting tissues. Symptoms include scorched, curled leaves, defoliation and heavy seed production.


    Verticillium wilt can be fatal to trees, and because the fungus exists in the soil, the only way to ensure it doesn’t infect replacement trees is to plant species that are resistant to the fungus.


    So what’s the prognosis for Port Washington’s maples?


    “There’s no doubt these trees are stressed, but hopefully they should be OK,” Witthun said.


    Not all of them.


    Crain estimated there are a couple dozen maples in the city, some of which are towering trees as old as they are tall, that are dead or beyond saving. Those include a number of mature maples along Grand Avenue just north of Summit Drive that were stressed from drought and succumbed to root damage caused by recent road construction, he said.


    “It’s not a wave of sudden die off, but rather just a slow death of some of our maples,” he said. “There are a number on the north end of the city, some that are 30 and 40 years old, that are in really rough shape.


    “I’ve been holding off as long as I can. I don’t want to take too many maples down with what’s happening to our ash trees, but we had to take some down because it got to the point where there was nothing left of the trees.”


    There’s no cure-all for the city’s maples — and experts point out it’s not just maples that are suffering — but there are a few things that experts say can be done to help stressed trees.


    “Give them some water,” Witthun said.


    She also recommended mulching with wood chips from the base of the tree out to the drip line. In addition to aiding water retention, wood chips add nutrients to the soil.


    Crain is advising residents to rake, not mulch leaves. Mulching leaves puts funguses like tar spot into the soil, where it lives throughout the winter. Come spring, it is ready to infect trees again.


    “Our municipal forests are always under some sort of stress,” Wendt said. “There’s a number of factors at work this year, but none of them is as bad as Port’s major problem — the emerald ash borer.”


Image Information: HOLDING LEAVES he picked off the grass, Port Washington Arborist Jon Crain stood next to a dying Norway maple on East Whitefish Road Tuesday. The tree, which Crain said could be 50 years old, is suffering the effects of drought, funguses and girdling roots like other maples in the city.   Photo by Bill Schanen IV

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